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What is the reason that the windows of ships' bridges are always inclined as shown in the above picture? | Look at CandiedOrange's answer
This answer was accepted, but CandiedOrange has the right answer. See this document page 21:
The second way in which reflection can interfer e with controller’s vision is light sources within the cab (or direct sunlight that enters the cab), which can cause disturbing refle... | https://api.stackexchange.com |
Several gene set enrichment methods are available, the most famous/popular is the Broad Institute tool. Many other tools are available (See for example the biocView of GSE which list 82 different packages). There are several parameters in consideration :
the statistic used to order the genes,
if it competitive or sel... | According to the FGSEA preprint:
We ran reference GSEA with default parameters. The permutation number
was set to 1000, which means that for each input gene set 1000
independent samples were generated. The run took 100 seconds and
resulted in 79 gene sets with GSEA-adjusted FDR q-value of less than
10−2. All s... | https://api.stackexchange.com |
Why are nearly all amino acids in organisms left-handed (exception is glycine which has no isomer) when abiotic samples typical have an even mix of left- and right-handed molecules? | I know that you are referring to the commonly ribosome-translated L-proteins, but I can't help but add that there are some peptides, called nonribosomal peptides, which are not dependent on the mRNA and can incorporate D-amino acids. They have very important pharmaceutical properties. I recommend this (1) review articl... | https://api.stackexchange.com |
What is the difference between thermodynamic and kinetic stability? I'd like a basic explanation, but not too simple. For example, methane does not burn until lit -- why? | To understand the difference between kinetic and thermodynamic stability, you first have to understand potential energy surfaces, and how they are related to the state of a system.
A potential energy surface is a representation of the potential energy of a system as a function of one or more of the other dimensions of ... | https://api.stackexchange.com |
In "Surely You're Joking, Mr. Feynman!," Nobel-prize winning Physicist Richard Feynman said that he challenged his colleagues to give him an integral that they could evaluate with only complex methods that he could not do with real methods:
One time I boasted, "I can do by other methods any integral anybody else needs... | I doubt that we will ever know the exact integral that vexed Feynman.
Here is something similar to what he describes.
Suppose $f(z)$ is an analytic function on the unit disk.
Then, by Cauchy's integral formula,
$$\oint_\gamma \frac{f(z)}{z}dz = 2\pi i f(0),$$
where $\gamma$ traces out the unit circle in a counterclockw... | https://api.stackexchange.com |
I have to do cross correlation of two audio file to prove they are similar.
I have taken the FFT of the two audio files and have their power spectrum values in separate arrays.
How should I proceed further to cross-correlate them and prove that they're similar? Is there a better way to do it? Any basic ideas will be h... | Cross-correlation and convolution are closely related. In short, to do convolution with FFTs, you
zero-pad the input signals a and b (add zeros to the end of each. The zero padding should fill the vectors until they reach a size of at least N = size(a)+size(b)-1)
take the FFT of both signals
multiply the results toge... | https://api.stackexchange.com |
Last night my daughter was asking why a mirror "always does that" (referring to reflecting a spot of light). To help her figure it out, I grabbed my green laser pointer so she could see the light traveling from the source and reflecting off the mirror.
But as we were playing, I noticed something strange.
Rather than on... | You are getting reflections from the front (glass surface) and back (mirrored) surface, including (multiple) internal reflections:
It should be obvious from this diagram that the spots will be further apart as you move to a more glancing angle of incidence. Depending on the polarization of the laser pointer, there is ... | https://api.stackexchange.com |
I do not remember precisely what the equations or who the relevant mathematicians and physicists were, but I recall being told the following story. I apologise in advance if I have misunderstood anything, or just have it plain wrong. The story is as follows.
A quantum physicist created some equations to
model what w... | The planet Neptune's discovery was an example of something similar to this. It was known that Newtons's Equations gave the wrong description of the motion of Uranus and Mercury. Urbain Le Verrier sat down and tried to see what would happen if we assumed that the equations were right and the universe was wrong. He set u... | https://api.stackexchange.com |
There is an obvious difference between finite difference and the finite volume method (moving from point definition of the equations to integral averages over cells). But I find FEM and FVM to be very similar; they both use integral form and average over cells.
What is the FEM method doing that the FVM is not? I have r... | Finite Element: volumetric integrals, internal polynomial order
Classical finite element methods assume continuous or weakly continuous approximation spaces and ask for volumetric integrals of the weak form to be satisfied. The order of accuracy is increased by raising the approximation order within elements. The met... | https://api.stackexchange.com |
I just came back from my Number Theory course, and during the lecture there was mention of the Collatz Conjecture.
I'm sure that everyone here is familiar with it; it describes an operation on a natural number – $n/2$ if it is even, $3n+1$ if it is odd.
The conjecture states that if this operation is repeated, all numb... | Another example: Euler's sum of powers conjecture, a generalization of Fermat's Last Theorem. It states:
If the equation $\sum_{i=1}^kx_i^n=z^n$ has a solution in positive integers, then $n \leq k$ (unless $k=1$). Fermat's Last Theorem is the $k=2$ case of this conjecture.
A counterexample for $n=5$ was found in 1966: ... | https://api.stackexchange.com |
As Wikipedia says:
[...] the kinetic energy of a non-rotating object of mass $m$ traveling at a speed $v$ is $\frac{1}{2}mv^2$.
Why does this not increase linearly with speed? Why does it take so much more energy to go from $1\ \mathrm{m/s}$ to $2\ \mathrm{m/s}$ than it does to go from $0\ \mathrm{m/s}$ to $1\ \mathr... | The previous answers all restate the problem as "Work is force dot/times distance". But this is not really satisfying, because you could then ask "Why is work force dot distance?" and the mystery is the same.
The only way to answer questions like this is to rely on symmetry principles, since these are more fundamental ... | https://api.stackexchange.com |
I understand that GPUs are generally used to do LOTS of calculations in parallel. I understand why we would want to parallelize processes in order to speed things up. However, GPUs aren't always better than CPUs, as far as I know.
What kinds of tasks are GPUs bad at? When would we prefer CPU over GPU for processing? | GPUs are bad at doing one thing at a time. A modern high-end GPU may have several thousand cores, but these are organized into SIMD blocks of 16 or 32. If you want to compute 2+2, you might have 32 cores each compute an addition operation, and then discard 31 of the results.
GPUs are bad at doing individual things fa... | https://api.stackexchange.com |
Okay, so everyone knows the usual methods of solving integrals, namely u-substitution, integration by parts, partial fractions, trig substitutions, and reduction formulas. But what else is there? Every time I search for "Advanced Techniques of Symbolic Integration" or "Super Advanced Integration Techniques", I get the ... | Here are a few. The first one is included because it's not very well known and is not general, though the ones that follow are very general and very useful.
A great but not very well known way to find the primitive of $f^{-1}$ in terms of the primitive of $f$, $F$, is (very easy to prove: just differentiate both sid... | https://api.stackexchange.com |
When people get sick, they often develop a fever. What is the effect of an increased body temperature on viruses and bacteria in the body? Is it beneficial to the infected body? Importantly, often fever-reducing agents like aspirin are prescribed when people are sick. Doesn't this counteract any benefits of fever? | Fever is a trait observed in warm and cold-blooded vertebrates that has been conserved for hundreds of millions of years (Evans, 2015).
Elevated body temperature stimulates the body's immune response against infectious viruses and bacteria. It also makes the body less favorable as a host for replicating viruses and ba... | https://api.stackexchange.com |
I have a bag of about 50 non-rechargeable AA batteries (1.5 V) that I have collected over the years. I bought a multimeter recently and would like to know the best way to test these batteries to determine which ones I should keep and which I should toss.
Sometimes a battery will be useless for certain high-power devic... | **WARNING: Lithium Ion cells **
While this question relates to non-rechargeable AA cells it is possible that someone may seek to extend the advice to testing other small cells.
In the case Of Li-Ion rechargeable cells (AA, 18650, other) this can be a very bad idea in some cases.
Shorting Lithium Ion cells as in test ... | https://api.stackexchange.com |
The AIC and BIC are both methods of assessing model fit penalized for the number of estimated parameters. As I understand it, BIC penalizes models more for free parameters than does AIC. Beyond a preference based on the stringency of the criteria, are there any other reasons to prefer AIC over BIC or vice versa? | Your question implies that AIC and BIC try to answer the same question, which is not true. The AIC tries to select the model that most adequately describes an unknown, high dimensional reality. This means that reality is never in the set of candidate models that are being considered. On the contrary, BIC tries to find... | https://api.stackexchange.com |
TV documentaries invariably show the Big Bang as an exploding ball of fire expanding outwards. Did the Big Bang really explode outwards from a point like this? If not, what did happen? | The simple answer is that no, the Big Bang did not happen at a point. Instead, it happened everywhere in the universe at the same time. Consequences of this include:
The universe doesn't have a centre: the Big Bang didn't happen at a point so there is no central point in the universe that it is expanding from.
The un... | https://api.stackexchange.com |
I often hear people talking about parallel computing and distributed computing, but I'm under the impression that there is no clear boundary between the 2, and people tend to confuse that pretty easily, while I believe it is very different:
Parallel computing is more tightly coupled to multi-threading, or how to make ... | This is partly a matter of terminology, and as such, only requires that you and the person you're talking to clarify it beforehand. However, there are different topics that are more strongly associated with parallelism, concurrency, or distributed systems.
Parallelism is generally concerned with accomplishing a particu... | https://api.stackexchange.com |
Searching an array of $N$ elements using binary search takes, in the worst case $\log_2 N$ iterations because, at each step we trim half of our search space.
If, instead, we used 'ternary search', we'd cut away two-thirds of our search space at each iteration, so the worst case should take $\log_3 N < \log_2 N$ iterat... | If you apply binary search, you have $$\log_2(n)+O(1)$$ many comparisons. If you apply ternary search, you have $$ 2 \cdot \log_3(n) + O(1)$$ many comparisons, as in each step, you need to perform 2 comparisons to cut the search space into three parts. Now if you do the math, you can observe that:
$$ 2 \cdot \log_3(n)... | https://api.stackexchange.com |
In a galvanic (voltaic) cell, the anode is considered negative and the cathode is considered positive. This seems reasonable as the anode is the source of electrons and cathode is where the electrons flow.
However, in an electrolytic cell, the anode is taken to be positive while the cathode is now negative. However, th... | The anode is the electrode where the oxidation reaction
\begin{align}
\ce{Red -> Ox + e-}
\end{align}
takes place while the cathode is the electrode where the reduction reaction
\begin{align}
\ce{Ox + e- -> Red}
\end{align}
takes place. That's how cathode and anode are defined.
Galvanic cell
Now, in a galvanic cell t... | https://api.stackexchange.com |
After reading a dataset:
dataset <- read.csv("forR.csv")
How can I get R to give me the number of cases it contains?
Also, will the returned value include of exclude cases omitted with na.omit(dataset)? | dataset will be a data frame. As I don't have forR.csv, I'll make up a small data frame for illustration:
set.seed(1)
dataset <- data.frame(A = sample(c(NA, 1:100), 1000, rep = TRUE),
B = rnorm(1000))
> head(dataset)
A B
1 26 0.07730312
2 37 -0.29686864
3 57 -1.18324224
4 91 0.0112... | https://api.stackexchange.com |
This question is an extension of two discussions that came up recently in the replies to "C++ vs Fortran for HPC". And it is a bit more of a challenge than a question...
One of the most often-heard arguments in favor of Fortran is that the compilers are just better. Since most C/Fortran compilers share the same back en... | The difference in your timings seems to be due to the manual unrolling of the unit-stride Fortran daxpy. The following timings are on a 2.67 GHz Xeon X5650, using the command
./test 1000000 10000
Intel 11.1 compilers
Fortran with manual unrolling: 8.7 sec
Fortran w/o manual unrolling: 5.8 sec
C w/o manual unrolling: 5... | https://api.stackexchange.com |
Here is a question for image processing experts.
I am working on a difficult computer vision problem. The task is to count the stomata (marked below) in DIC microscopy images. These images are resistant to most superficial image processing techniques like morphological operations and edge detection. It is also differ... | Sorry I don't know OpenCV, and this is more a pre-processing step than a complete answer:
First, you don't want an edge detector. An edge detector converts transitions (like this dark-to-light):
into ridges (bright lines on dark) like this:
It performs a differentiation, in other words.
But in your images, there is ... | https://api.stackexchange.com |
I am a bit confused. What is the difference between a linear and affine function? Any suggestions will be appreciated. | A linear function fixes the origin, whereas an affine function need not do so. An affine function is the composition of a linear function with a translation, so while the linear part fixes the origin, the translation can map it somewhere else.
Linear functions between vector spaces preserve the vector space structure (... | https://api.stackexchange.com |
Many times, when I've inherited or encountered scientific code written by other people (or occasionally, even my own work), I've noticed that documentation is either sparse or nonexistent. If I'm lucky, I see informative comments. If I'm very lucky, there's even Doxygen comments and a Doxyfile so that I have function i... | I think that documentation for scientific software can be divided into three categories, all of which are necessary for full understanding. The easiest and most common is individual method documentation. There are many systems for this. You mention doxygen, Python has pydoc, and in PETSc we have our own package sowing ... | https://api.stackexchange.com |
There have been various explanations posited for the α-effect. The α-effect refers to a phenomenon wherein nucleophiles with lone pairs on atoms adjacent (i.e., in the α- position) to the atom bearing the reacting lone pair sometimes exhibit dramatically higher reactivity than similar nucleophiles without α-electrons. ... | I am not a kineticist, and my quantum chemistry is long, long out of date, but what I was about to say was that I'd guess the reason the "effect" is "unsolved" is that it's not real.
That is, it is not a property of a single reactant while disregarding its environment (gas phase, solvent interactions). Then I saw that... | https://api.stackexchange.com |
I recently purchased a Weller WES51 soldering iron as my first temperature controlled iron and I'm looking for recommendations on the best default temperature to use when soldering.
I'm using mainly .031 inch 60/40 solder on through-hole components. | What’s the proper soldering iron temperature for standard .031" 60/40 solder?
There is no proper soldering iron temperature just for a given type of solder - the iron temperature should be set for both the component and the solder.
When soldering surface mount components, a small tip and 600F (315C) should be sufficie... | https://api.stackexchange.com |
I know how to downsample a BAM file to lower coverage. I know I can randomly select lines in SAM, but this procedure can't guarantee two reads in a pair are always sampled the same time. Is there a way to downsample BAM while keeping pairing information intact? | samtools has a subsampling option:
-s FLOAT:
Integer part is used to seed the random number generator [0]. Part after the decimal point sets the fraction of templates/pairs to subsample [no subsampling]
samtools view -bs 42.1 in.bam > subsampled.bam
will subsample 10 percent mapped reads with 42 as the seed for t... | https://api.stackexchange.com |
I have become a bit confused about these topics. They've all started looking the same to me. They seem to have the same properties such as linearity, shifting and scaling associated with them. I can't seem to put them separately and identify the purpose of each transform. Also, which one of these is used for frequency ... | The Laplace and Fourier transforms are continuous (integral) transforms of continuous functions.
The Laplace transform maps a function \$f(t)\$ to a function \$F(s)\$ of the complex variable s, where \$s = \sigma + j\omega\$.
Since the derivative \$\dot f(t) = \frac{df(t)}{dt} \$ maps to \$sF(s)\$, the Laplace transfor... | https://api.stackexchange.com |
Well, we've got favourite statistics quotes. What about statistics jokes? | A guy is flying in a hot air balloon and he's lost. So he lowers himself over a field and shouts to a guy on the ground:
"Can you tell me where I am, and which way I'm headed?"
"Sure! You're at 43 degrees, 12 minutes, 21.2 seconds north; 123 degrees, 8 minutes, 12.8 seconds west. You're at 212 meters above sea level. ... | https://api.stackexchange.com |
Most books refer to a steep rise in pH when a titration reaches the equivalence point. However, I do not understand why … I mean I am adding the same drops of acid to the alkali but just as I near the correct volume (i.e. the volume required to neutralize the alkali), the pH just suddenly increases quickly. | I've decided to tackle this question in a somewhat different manner. Instead of giving the chemical intuition behind it, I wanted to check for myself if the mathematics actually work out. As far as I understand, this isn't done often, so that's why I wanted to try it, even though it may not make the clearest answer. It... | https://api.stackexchange.com |
For a project I am working on (in hyperbolic PDEs) I would like to get some rough handle on the behavior by looking at some numerics. I am, however, not a very good programmer.
Can you recommend some resources for learning how to effectively code finite difference schemes in Scientific Python (other languages with sma... | Here is a 97-line example of solving a simple multivariate PDE using finite difference methods, contributed by Prof. David Ketcheson, from the py4sci repository I maintain. For more complicated problems where you need to handle shocks or conservation in a finite-volume discretization, I recommend looking at pyclaw, a ... | https://api.stackexchange.com |
What tradeoffs should I consider when deciding to use an SPI or I2C interface?
This accelerometer/gyro breakout board is available in two models, one for each interface. Would either one be easier to integrate into an Arduino project? | Summary
SPI is faster.
I2C is more complex and not as easy to use if your microcontroller doesn't have an I2C controller.
I2C only requires 2 lines.
I2C is a bus system with bidirectional data on the SDA line. SPI is a point-to-point connection with data in and data out on separate lines (MOSI and MISO).
Essen... | https://api.stackexchange.com |
I would like to select a random record from a large set of n unaligned sequencing reads in log(n) time complexity (big O notation) or less. A record is defined as the equivalent of four lines in FASTQ format. The records do not fit in RAM and would need to be stored on disk. Ideally, I would like to store the reads in ... | Arbitrary record access in constant time
To get a random record in constant time, it is sufficient to get an arbitrary record in constant time.
I have two solutions here: One with tabix and one with grabix. I think the grabix solution is more elegant, but I am keeping the tabix solution below because tabix is a more ma... | https://api.stackexchange.com |
I am looking for fun, interesting mathematics textbooks which would make good studious holiday gifts for advanced mathematics undergraduates or beginning graduate students. They should be serious but also readable.
In particular, I am looking for readable books on more obscure topics not covered in a standard undergra... | Check into Generatingfunctionology by Herbert Wilf. From the linked (author's) site, the second edition is available for downloading as a pdf. There is also a link to the third edition, available for purchase. It's a very helpful, useful, readable, fun, (and short!) book that a student could conceivably cover over wint... | https://api.stackexchange.com |
My teacher told me about resonance and explained it as different structures which are flipping back and forth and that we only observe a sort of average structure. How does this work? Why do the different structures not exist on their own? | This answer is intended to clear up some misconceptions about resonance which have come up many times on this site.
Resonance is a part of valence bond theory which is used to describe delocalised electron systems in terms of contributing structures, each only involving 2-centre-2-electron bonds. It is a concept that i... | https://api.stackexchange.com |
I saw in a SO thread a suggestion to use filtfilt which performs backwards/forwards filtering instead of lfilter.
What is the motivation for using one against the other technique? | filtfilt is zero-phase filtering, which doesn't shift the signal as it filters. Since the phase is zero at all frequencies, it is also linear-phase. Filtering backwards in time requires you to predict the future, so it can't be used in "online" real-life applications, only for offline processing of recordings of sign... | https://api.stackexchange.com |
I used to work with publicly available genomic references, where basic statistics are usually available and if they are not, you have to compute them only once so there is no reason to worry about performance.
Recently I started sequencing project of couple of different species with mid-sized genomes (~Gbp) and during ... | For FASTQ:
seqtk fqchk in.fq | head -2
It gives you percentage of "N" bases, not the exact count, though.
For FASTA:
seqtk comp in.fa | awk '{x+=$9}END{print x}'
This command line also works with FASTQ, but it will be slower as awk is slow.
EDIT: ok, based on @BaCH's reminder, here we go (you need kseq.h to compile):... | https://api.stackexchange.com |
We've learnt that the electropositive element is written first. Then why is ammonia written as $\ce{NH3}$ ? | According to current nomenclature rules, $\ce{H3N}$ would be correct and acceptable. However some chemical formulas, like $\ce{NH3}$ for ammonia, that were in use long before the rules came out, are still accepted today. | https://api.stackexchange.com |
Are there any tools in Python that are like Matlab's parfor? I found this thread, but it's four years old. I thought maybe someone here might have more recent experience.
Here's an example of the type of thing I'd like to parallelize:
X = np.random.normal(size=(10, 3))
F = np.zeros((10, ))
for i in range(10):
F[i]... | Joblib does what you want.
The basic usage pattern is:
from joblib import Parallel, delayed
def myfun(arg):
do_stuff
return result
results = Parallel(n_jobs=-1, verbose=verbosity_level, backend="threading")(
map(delayed(myfun), arg_instances))
where arg_instances is list of values for which my... | https://api.stackexchange.com |
It seems that everywhere I look, data structures are being implemented using red-black trees (std::set in C++, SortedDictionary in C#, etc.)
Having just covered (a,b), red-black & AVL trees in my algorithms class, here's what I got out (also from asking around professors, looking through a few books and googling a bit)... | To quote from the answer to “Traversals from the root in AVL trees and Red Black Trees” question
For some kinds of binary search trees, including red-black trees but
not AVL trees, the "fixes" to the tree can fairly easily be predicted
on the way down and performed during a single top-down pass, making
the secon... | https://api.stackexchange.com |
I agree that a Turing Machine can do "all possible mathematical problems". But that is because it is just a machine representation of an algorithm: first do this, then do that, finally output that.
I mean anything that is solvable can be represented by an algorithm (because that is precisely the definition of 'solvabl... | I agree that a Turing Machine can do "all the possible mathematical problems".
Well, you shouldn't, because it's not true. For example, Turing machines cannot determine if polynomials with integer coefficients have integer solutions (Hilbert's tenth problem).
Is Turing Machine “by definition” the most powerful machin... | https://api.stackexchange.com |
Standard finite difference formulas are usable to numerically compute a derivative under the expectation that you have function values $f(x_k)$ at evenly spaced points, so that $h \equiv x_{k+1} - x_k$ is a constant. What if I have unevenly spaced points, so that $h$ now varies from one pair of adjacent points to the n... | J.M's comment is right: you can find an interpolating polynomial and differentiate it. There are other ways of deriving such formulas; typically, they all lead to solving a van der Monde system for the coefficients. This approach is problematic when the finite difference stencil includes a large number of points, bec... | https://api.stackexchange.com |
I think I remember reading somewhere that the Baire Category Theorem is supposedly quite powerful. Whether that is true or not, it's my favourite theorem (so far) and I'd love to see some applications that confirm its neatness and/or power.
Here's the theorem (with proof) and two applications:
(Baire) A non-empty comp... | If $P$ is an infinitely differentiable function such that for each $x$, there is an $n$ with $P^{(n)}(x)=0$, then $P$ is a polynomial. (Note $n$ depends on $x$.) See the discussion in Math Overflow. | https://api.stackexchange.com |
I am a CS undergraduate. I understand how Turing came up with his abstract machine (modeling a person doing a computation), but it seems to me to be an awkward, inelegant abstraction. Why do we consider a "tape", and a machine head writing symbols, changing state, shifting the tape back and forth?
What is the underlyi... | Well, a DFA is just a Turing machine that's only allowed to move to the right and that must accept or reject as soon as it runs out of input characters. So I'm not sure one can really say that a DFA is natural but a Turing machine isn't.
Critique of the question aside, remember that Turing was working before computers ... | https://api.stackexchange.com |
I am seeking help understanding Floyd's cycle detection algorithm. I have gone through the explanation on wikipedia (
I can see how the algorithm detects cycle in O(n) time. However, I am unable to visualise the fact that once the tortoise and hare pointers meet for the first time, the start of the cycle can be determi... | You can refer to "Detecting start of a loop in singly linked list", here's an excerpt:
Distance travelled by slowPointer before meeting $= x+y$
Distance travelled by fastPointer before meeting $=(x + y + z) + y = x + 2y + z$
Since fastPointer travels with double the speed of slowPointer, and time is constant for both ... | https://api.stackexchange.com |
I've always wondered why processors stopped at 32 registers. It's by far the fastest piece of the machine, why not just make bigger processors with more registers? Wouldn't that mean less going to the RAM? | First, not all processor architectures stopped at 32 registers. Almost all the RISC architectures that have 32 registers exposed in the instruction set actually have 32 integer registers and 32 more floating point registers (so 64). (Floating point "add" uses different registers than integer "add".) The SPARC archite... | https://api.stackexchange.com |
I'm training a neural network but the training loss doesn't decrease. How can I fix this?
I'm not asking about overfitting or regularization. I'm asking about how to solve the problem where my network's performance doesn't improve on the training set.
A specific variant of this problem arises when the loss has a steep ... | 1. Verify that your code is bug free
There's a saying among writers that "All writing is re-writing" -- that is, the greater part of writing is revising. For programmers (or at least data scientists) the expression could be re-phrased as "All coding is debugging."
Any time you're writing code, you need to verify that ... | https://api.stackexchange.com |
I am trying to design a cloth that, from the point of view of a camera, is very difficult to compress with JPG, resulting in big-size files (or leading to low image quality if file size is fixed).
It must work even if the cloth is far away from the camera, or rotated (let's say the scale can vary from 1x to 10x).
Noise... | Noise is quite good (hard to compress), but it becomes grey when looking from far, becoming easy to compress. A good pattern would be kind of fractal, looking similar at all scales.
Well, there is fractal noise. I think Brownian noise is fractal, looking the same as you zoom into it. Wikipedia talks about adding Per... | https://api.stackexchange.com |
Red-green colorblindness seems to make it harder for a hunter-gatherer to see whether a fruit is ripe and thus worth picking.
Is there a reason why selection hasn't completely removed red-green color blindness? Are there circumstances where this trait provides an evolutionary benefit? | Short answer
Color-blind subjects are better at detecting color-camouflaged objects. This may give color blinds an advantage in terms of spotting hidden dangers (predators) or finding camouflaged foods.
Background
There are two types of red-green blindness: protanopia (red-blind) and deuteranopia (green-blind), i.e., t... | https://api.stackexchange.com |
TL:DR: Is it ever a good idea to train an ML model on all the data available before shipping it to production? Put another way, is it ever ok to train on all data available and not check if the model overfits, or get a final read of the expected performance of the model?
Say I have a family of models parametrized by $... | The way to think of cross-validation is as estimating the performance obtained using a method for building a model, rather than for estimating the performance of a model.
If you use cross-validation to estimate the hyperparameters of a model (the $\alpha$s) and then use those hyper-parameters to fit a model to the whol... | https://api.stackexchange.com |
A diode is put in parallel with a relay coil (with opposite polarity) to prevent damage to other components when the relay is turned off.
Here's an example schematic I found online:
I'm planning on using a relay with a coil voltage of 5V and contact rating of 10A.
How do I determine the required specifications for t... | First determine the coil current when the coil is on. This is the current that will flow through the diode when the coil is switched off. In your relay, the coil current is shown as 79.4 mA. Specify a diode for at least 79.4 mA current. In your case, a 1N4001 current rating far exceeds the requirement.
The diode rever... | https://api.stackexchange.com |
Sometimes men wake up with an erection in the morning. Why does this happen? | Sometimes men wake up with an erection in the morning. Why does this happen?
Shortly speaking: REM (Rapid Eye Movement) is one phase of sleep. During this phase, we dream and some of our neurotransmitters are shut off. This include norepinephrine, which is involved in controlling erections. Norepinephrine prevents bloo... | https://api.stackexchange.com |
Does anyone have recommendations on a usable, fast C++ matrix library?
What I mean by usable is the following:
Matrix objects have an intuitive interface (ex.: I can use rows and columns while indexing)
I can do anything with the matrix class that I can do with LAPACK and BLAS
Easy to learn and use API
Relatively pain... | I've gathered the following from online research so far:
I've used Armadillo a little bit, and found the interface to be intuitive enough, and it was easy to locate binary packages for Ubuntu (and I'm assuming other Linux distros). I haven't compiled it from source, but my hope is that it wouldn't be too difficult. It ... | https://api.stackexchange.com |
What the difference between TPM and CPM when dealing with RNA seq data?
What metrics would you use if you have to perform some down stream analysis other than Differential expression for eg.
Clustering analysis using Hclust function and then plotting heat map to find differences in terms of expression levels, correlat... | You can find the various equations in this oft-cited blog post from Harold Pimentel. CPM is basically depth-normalized counts, whereas TPM is length-normalized (and then normalized by the length-normalized values of the other genes).
If one has to choose between those two choices one typically chooses TPM for most thin... | https://api.stackexchange.com |
My textbook mentions that SCUBA tanks often contain a mixture of oxygen and nitrogen along with a little helium which serves as a diluent.
Now as I remember it, divers take care not to surface too quickly because it results in 'the Bends', which involves the formation of nitrogen bubbles in the blood and is potentiall... | The other answers here, describing oxygen toxicity are telling what can go wrong if you have too much oxygen, but they are not describing two important concepts that should appear with their descriptions. Also, there is a basic safety issue with handling pressure tanks of high oxygen fraction.
An important property of ... | https://api.stackexchange.com |
Does anyone know of a freeware SPICE / circuit simulator?
SPICE (Simulation Program with Integrated Circuit Emphasis) is a general-purpose, open source analog electronic circuit simulator. It is a powerful program that is used in integrated circuit and board-level design to check the integrity of circuit designs and ... | ngSpice is available for gEDA.
gnuCAP is also available for gEDA.
LTSpice is free from Linear Technology.
I thought that one of the other analog chip makers had a spice too but I can't remember
who :(
I have been to a few talks on simulation given by physicists and EEs who have done
chip design. Each of the talks see... | https://api.stackexchange.com |
The sensitive plant (Mimosa pudica) is a remarkable little plant whose characteristic feature is its ability to droop its leaves when disturbed:
Apparently, this ability to droop rests on the cells in the leaves of the sensitive plant being able to draw water out of themselves through changes in intracellular ion conc... | In fact, the idea of a plant nervous system is quite serious and constantly developing; of course those are rather local, simple signal pathways rather than an "animalian" centralized global network, but they use similar mechanisms -- depolarisation waves, neurotransmitter-like compounds, specialized cells... Here is a... | https://api.stackexchange.com |
For a molecule to have a smell it's necessary that the molecule be volatile enough to be in the air. So I think that excludes molecules which are solid at room temperature and atmospheric pressure. Maybe the question then is equivalent to: what is the highest molecular weight organic compound which is liquid at room te... | I'll quote from $\ce{[1]}$:
The general requirements for an odorant are that it should be
volatile, hydrophobic and have a molecular weight less than
approximately 300 daltons. Ohloff (1994) has stated that the largest
known odorant is a labdane with a molecular weight of 296. The first
two requirements make physical ... | https://api.stackexchange.com |
In single-cell RNA-seq data we have an inflated number of 0 (or near-zero) counts due to low mRNA capture rate and other inefficiencies.
How can we decide which genes are 0 due to gene dropout (lack of measurement sensitivity), and which are genuinely not expressed in the cell?
Deeper sequencing does not solve this pro... | Actually this is one of the main problems you have when analyzing scRNA-seq data, and there is no established method for dealing with this. Different (dedicated) algorithms deal with it in different ways, but mostly you rely on how good the error modelling of your software is (a great read is the review by Wagner, Rege... | https://api.stackexchange.com |
I've just finished a Classical Mechanics course, and looking back on it some things are not quite clear. In the first half we covered the Lagrangian formalism, which I thought was pretty cool. I specially appreciated the freedom you have when choosing coordinates, and the fact that you can basically ignore constraint f... | There are several reasons for using the Hamiltonian formalism:
Statistical physics. The standard thermal states weight of pure states is given according to
$$\text{Prob}(\text{state}) \propto e^{-H(\text{state})/k_BT}$$
So you need to understand Hamiltonians to do stat mech in real generality.
Geometrical prettiness... | https://api.stackexchange.com |
In evaluating the quality of a piece of software you are about to use (whether it's something you wrote or a canned package) in computational work, it is often a good idea to see how well it works on standard data sets or problems. Where might one obtain these tests for verifying computational routines?
(One website/bo... | If you are interested in conducting an analysis on sparse matrices, I would also consider Davis's University of Florida Sparse Matrix Collection and the Matrix Market. | https://api.stackexchange.com |
I haven't yet gotten a good answer to this: If you have two rays of light of the same wavelength and polarization (just to make it simple for now, but it easily generalizes to any range and all polarizations) meet at a point such that they're 180 degrees out of phase (due to path length difference, or whatever), we all... | First let's deal with a false assumption:
similar to the way that the sum of a huge number of randomly selected 1's and -1's would never stray far from 0.
Suppose we have a set of $N$ random variables $X_i$, each independent and with equal probability of being either $+1$ or $-1$. Define
$$ S = \sum_{i=1}^N X_i. $$
T... | https://api.stackexchange.com |
A few years ago, MapReduce was hailed as revolution of distributed programming. There have also been critics but by and large there was an enthusiastic hype. It even got patented! [1]
The name is reminiscent of map and reduce in functional programming, but when I read (Wikipedia)
Map step: The master node takes the in... | I can not help but think: this is divide & conquer, plain and simple!
M/R is not divide & conquer. It does not involve the repeated application of an algorithm to a smaller subset of the previous input. It's a pipeline (a function specified as a composition of simpler functions) where pipeline stages are alternating ... | https://api.stackexchange.com |
I've implemented a gaussian blur fragment shader in GLSL. I understand the main concepts behind all of it: convolution, separation of x and y using linearity, multiple passes to increase radius...
I still have a few questions though:
What's the relationship between sigma and radius?
I've read that sigma is equivalent ... | What's the relationship between sigma and radius? I've read that sigma is equivalent to radius, I don't see how sigma is expressed in pixels. Or is "radius" just a name for sigma, not related to pixels?
There are three things at play here. The variance, ($\sigma^2$), the radius, and the number of pixels. Since this is... | https://api.stackexchange.com |
I've seen lots of schematics use \$V_{CC}\$ and \$V_{DD}\$ interchangeably.
I know \$V_{CC}\$ and \$V_{DD}\$ are for positive voltage, and \$V_{SS}\$ and \$V_{EE}\$ are for ground, but what is the difference between each of the two?
Do the \$C\$, \$D\$, \$S\$, and \$E\$ stand for something?
For extra credit: Why ... | Back in the pleistoscene (1960s or earlier), logic was implemented with bipolar transistors. Even more specifically, they were NPN because for some reasons I'm not going to get into, NPN were faster. Back then it made sense to someone that the positive supply voltage would be called Vcc where the "c" stands for colle... | https://api.stackexchange.com |
The purpose of this question is to ask about the role of mathematical rigor in physics. In order to formulate a question that can be answered, and not just discussed, I divided this large issue into five specific questions.
Update February, 12, 2018: Since the question was put yesterday on hold as too board, I ask futu... | Rigorous arguments are very similar to computer programming--- you need to write a proof which can (in principle) ultimately be carried out in a formal system. This is not easy, and requires defining many data-structures (definitions), and writing many subroutines (lemmas), which you use again and again. Then you prove... | https://api.stackexchange.com |
I'm a mathematician who recently became very interested in questions related to mathematical physics but somehow, I faced difficulties in penetrating the literature... I'd highly appreciate any help with the following question:
My aim is to relate a certain (equivariant) linear sigma model on a disc (with a non-compac... | This is a reference resources question, masquerading as an answer, given the constraints of the site. The question hardly belongs here, and has been duplicated in the overflow cousin site . It might well be deleted.
There have been schools and proceedings on the subject,
Integrability: From Statistical Systems to Gauge... | https://api.stackexchange.com |
Today a friend's six year old sister asked me the question "why don't people on the other side of the earth fall off?". I tried to explain that the Earth is a huge sphere and there's a special force called "gravity" that tries to attract everything to the center of the Earth, but she doesn't seem to understand it. I al... | Having my own 6-year-old and having successfully explained this, here's my advice from experience:
Don't try to explain gravity as a mysterious force. It doesn't make sense to most adults (sad, but true! talk to non-physicists about it and you'll see), it won't make sense to a 6yo.
The reason this won't work is that i... | https://api.stackexchange.com |
I currently find Harvard's RESTful API for ExAC extremely useful and I was hoping that a similar resource is available for Gnomad?
Does anyone know of a public access API for Gnomad or possibly any plans to integrate Gnomad into the Harvard API? | As far as I know, no but the vcf.gz files are behind a http server that supports Byte-Range, so you can use tabix or any related API:
$ tabix " "22:17265182-17265182"
22 17265182 . A T 762.04 PASS AC=1;AF=4.78057e-06;AN=209180;BaseQRankSum=-4.59400e+00;ClippingRankSum=2.18000e+00;DP=4906893;FS=1.00270e+01... | https://api.stackexchange.com |
I am trying to understand the benefits of joint genotyping and would be grateful if someone could provide an argument (ideally mathematically) that would clearly demonstrate the benefit of joint vs. single-sample genotyping.
This is what I've gathered from other resources (Biostars, GATK forums, etc.)
Joint-genotyping... | Say you are sequencing to 2X coverage. Suppose at a site, sample S has one reference base and one alternate base. It is hard to tell if this is a sequencing error or a heterozygote. Now suppose you have 1000 other samples, all at 2X read depth. One of them has two ALT bases; 10 of them have one REF and one ALT. It is u... | https://api.stackexchange.com |
I'd be tempted to call nipples in men vestigial, but that suggests they have no modern function. They do have a function, of course, but only in women. So why do men (and all male mammals) have them? | I believe it is for this reason: the female body plan is the default one. Males are a variation upon that, in humans at least. Nipples are part of the basic body plan. For a man to not have them, he would need to actively evolve something that would prevent nipples from developing. There is no selective pressure for th... | https://api.stackexchange.com |
A lot of the organometallics are rather... interesting compounds to work with. The most famous (among those who care, anyway) is tert-butyllithium or t-BuLi. It is the textbook example of a pyrophoric substance, demonstrated to pretty much every chemistry major as an air-sensitive chemical requiring special handling (S... | Answering my own question based on the comments, tert-butyl-hydroperoxide is at least one such chemical. As stated on this MSDS from a government website, it's a 4-4-4, with additional special warning of being a strong oxidizer. The only thing that it does not do that could make the 704 diamond any worse is react stron... | https://api.stackexchange.com |
We have a random experiment with different outcomes forming the sample space $\Omega,$ on which we look with interest at certain patterns, called events $\mathscr{F}.$ Sigma-algebras (or sigma-fields) are made up of events to which a probability measure $\mathbb{P}$ can be assigned. Certain properties are fulfilled, in... | To Xi'an's first point: When you're talking about $\sigma$-algebras, you're asking about measurable sets, so unfortunately any answer must focus on measure theory. I'll try to build up to that gently, though.
A theory of probability admitting all subsets of uncountable sets will break mathematics
Consider this example.... | https://api.stackexchange.com |
I'm trying to download three WGS datasets from the SRA that are each between 60 and 100GB in size. So far I've tried:
Fetching the .sra files directly from NCBI's ftp site
Fetching the .sra files directly using the aspera command line (ascp)
Using the SRA toolkit's fastqdump and samdump tools
It's excruciatingly slo... | Proximity to NCBI may not necessarily give you the fastest transfer speed. AWS may be deliberately throttling the Internet connection to limit the likelihood that people will use it for undesirable things. There's a chance that a home network might be faster, but you're likely to get the fastest connection to NCBI by u... | https://api.stackexchange.com |
I'm interested working with the medication information provided by the UK Biobank. In order to get these into a usable form I would like to map them to ATC codes. Since many of the drugs listed in the data showcase include dosage information, doing an exact string match between drug names is not very effective. I've... | The CART tool let's you upload a set of names and map them (optionally in a fuzzy way) to STITCH 4 identifiers, and then use those to map to ATC codes (using the chemicals sources download file). It's a bit indirect, and I'm not sure what CART will do with the dosage info you mention. | https://api.stackexchange.com |
A friend of mine was looking over the definition of pH and was wondering if it is possible to have a negative pH. From the equation below, it certainly seems mathematically possible—if you have a $1.1$ (or something $\gt 1$) molar solution of $\ce{H+}$ ions:
$$\text{pH} = -\log([\ce{H+}])$$
(Where $[\ce{X}]$ denotes th... | One publication for you: “Negative pH Does Exist”, K. F. Lim, J. Chem. Educ. 2006, 83, 1465. Quoting the abstract in full:
The misconception that pH lies between 0 and 14 has been perpetuated in popular-science books, textbooks, revision guides, and reference books.
The article text provides some counterexamples:
Fo... | https://api.stackexchange.com |
Disclaimer: I'm not a statistician but a software engineer. Most of my knowledge in statistics comes from self-education, thus I still have many gaps in understanding concepts that may seem trivial for other people here. So I would be very thankful if answers included less specific terms and more explanation. Imagine t... | The short version is that the Beta distribution can be understood as representing a distribution of probabilities, that is, it represents all the possible values of a probability when we don't know what that probability is. Here is my favorite intuitive explanation of this:
Anyone who follows baseball is familiar with ... | https://api.stackexchange.com |
In my computational science PhD program, we are working almost exclusively in C++ and Fortran. It seems like some professors prefer one over the other. I am wondering which one is 'better' or if one is better than the other in a certain circumstance. | As so often, the choice depends on (1) the problem you are trying to solve, (2) the skills you have, and (3) the people you work with (unless it's a solo project). I'll leave (3) aside for the moment because it depends on everyone's individual situation.
Problem dependence: Fortran excels at array processing. If your p... | https://api.stackexchange.com |
What makes dimerization possible in $\ce{AlCl3}$? Are there 3c-2e bonds in $\ce{Al2Cl6}$ as there are in $\ce{B2H6}$? | Introduction
The bonding situation in $\ce{(AlCl3)2}$ and $\ce{(BCl3)2}$ is nothing trivial and the reason why aluminium chloride forms dimers, while boron trichloride does not, cannot only be attributed to size.
In order to understand this phenomenon we need to look at both, the monomers and the dimers, and compare th... | https://api.stackexchange.com |
My understanding is that light can not escape from within a black hole (within the event horizon). I've also heard that information cannot propagate faster than the speed of light. I assume that the gravitational attraction caused by a black hole carries information about the amount of mass within the black hole.
So, h... | There are some good answers here already but I hope this is a nice short summary:
Electromagnetic radiation cannot escape a black hole, because it travels at the speed of light. Similarly, gravitational radiation cannot escape a black hole either, because it too travels at the speed of light. If gravitational radiation... | https://api.stackexchange.com |
I've heard that the Hilbert transform can be used to calculate the envelope of a signal. How does this work? And how is this "Hilbert envelope" different from the envelope one gets by simply rectifying a signal?
I'm interested specifically in finding a way to calculate an envelope for use in dynamic range compression ... | The Hilbert transform is used to calculate the "analytic" signal. See for example If your signal is a sine wave or an modulated sine wave, the magnitude of the analytic signal will indeed look like the envelope. However, the computation of the Hilbert transform is not trivial. Technically it requires a non-causal FIR ... | https://api.stackexchange.com |
I know that the cells of mammals at least stop dividing when they are old, and then die a programmed cell death. Then other cells have to replace them.
But in a bacterial colony, each cell replicates for itself. Obviously, if a division of a bacterial cell of generation N were to produce two new cells of generation N+... | This is a interesting question and for a long time it was thought that they do not age. In the meantime there are some new papers which say that bacteria do indeed age.
Aging can be defined as the accumulation of non-genetic damages (for example oxidative damage to proteins) over time. If too much of these damages are ... | https://api.stackexchange.com |
If I write on the starting page of a notebook, it will write well. But when there are few or no pages below the page where I am writing, the pen will not write well. Why does this happen? | I'd say the culprit is the contact area between the two surfaces relative to the deformation.
When there are other pieces of paper below it, all the paper is able to deform when you push down; because the paper is fairly soft and deformable fiber. If there is more soft deformable paper below it, the layers are able to... | https://api.stackexchange.com |
I know how to code for factorials using both iterative and recursive (e.g. n * factorial(n-1) for e.g.). I read in a textbook (without been given any further explanations) that there is an even more efficient way of coding for factorials by dividing them in half recursively.
I understand why that may be the case. Howe... | The best algorithm that is known is to express the factorial as a product of prime powers. One can quickly determine the primes as well as the right power for each prime using a sieve approach. Computing each power can be done efficiently using repeated squaring, and then the factors are multiplied together. This wa... | https://api.stackexchange.com |
In my linear algebra class, we just talked about determinants. So far I’ve been understanding the material okay, but now I’m very confused. I get that when the determinant is zero, the matrix doesn’t have an inverse. I can find the determinant of a $2\times 2$ matrix by the formula. Our teacher showed us how to compute... | Your trouble with determinants is pretty common. They’re a hard thing to teach well, too, for two main reasons that I can see: the formulas you learn for computing them are messy and complicated, and there’s no “natural” way to interpret the value of the determinant, the way it’s easy to interpret the derivatives you d... | https://api.stackexchange.com |
What are the definitions of these three things and how are they related? I've tried looking online but there is no concrete answer online for this question. | Here's a graphic I use to explain the difference in my general chemistry courses:
All electrons that have the same value for $n$ (the principle quantum number) are in the same shell
Within a shell (same $n$), all electrons that share the same $l$ (the angular momentum quantum number, or orbital shape) are in the same... | https://api.stackexchange.com |
I am used to thinking of finite-differences as a special case of finite-elements, on a very constrained grid. So what are the conditions on how to choose between Finite Difference Method (FDM) and Finite Element Method (FEM) as a numerical method?
On the side of Finite Difference Method (FDM), one may count that they a... | It is possible to write most specific finite difference methods as Petrov-Galerkin finite element methods with some choice of local reconstruction and quadrature, and most finite element methods can also be shown to be algebraically equivalent to some finite difference method. Therefore, we should choose a method based... | https://api.stackexchange.com |
As part of some blockchain-related research I am currently undertaking, the notion of using blockchains for a variety of real-world applications are thrown about loosely.
Therefore, I propose the following questions:
What important/crucial real-world applications use blockchain?
To add on to the first question, more s... | Apart from Bitcoin and Ethereum (if we are generous) there are no major and
important uses today.
It is important to notice that blockchains have some severe limitations. A
couple of them being:
It only really works for purely digital assets
The digital asset under control needs to keep its value even if it's public
... | https://api.stackexchange.com |
I haven't seen the question stated precisely in these terms, and this is why I make a new question.
What I am interested in knowing is not the definition of a neural network, but understanding the actual difference with a deep neural network.
For more context: I know what a neural network is and how backpropagation wor... | Let's start with a triviliaty: Deep neural network is simply a feedforward network with many hidden layers.
This is more or less all there is to say about the definition. Neural networks can be recurrent or feedforward; feedforward ones do not have any loops in their graph and can be organized in layers. If there are "... | https://api.stackexchange.com |
If symmetry conditions are met, FIR filters have a linear phase. This is not true for IIR filters.
However, for what applications is it bad to apply filters that do not have this property and what would be the negative effect? | Let me add the following graphic to the great answers already given, with the intention of a specific and clear answer to the question posed. The other answers detail what linear phase is, this details why it is important in one graphic:
When a filter has linear phase, then all the frequencies within that signal will ... | https://api.stackexchange.com |
The situation
Some researchers would like to put you to sleep. Depending on the secret toss of a fair coin, they will briefly awaken you either once (Heads) or twice (Tails). After each waking, they will put you back to sleep with a drug that makes you forget that awakening. When you are awakened, to what degree sho... | Strategy
I would like to apply rational decision theory to the analysis, because that is one well-established way to attain rigor in solving a statistical decision problem. In trying to do so, one difficulty emerges as special: the alteration of SB’s consciousness.
Rational decision theory has no mechanism to handle ... | https://api.stackexchange.com |
I found two of these objects near a creek in Missouri. They feel like they are made out of bone but they do not look like any bone I have seen before. They also appear as though the could be some sort of plant part. I am having a very difficult time identifying them and any help would be appreciated. | Those are isolated turtle bones:
Specifically, they are part of the carapace, or upper shell. The projections would articulate with the backbone. The "toothlike" structure at the other end projects down toward the margin of the shell.
Based on the size, and the fact that you are in Missouri, I'm guessing they are snap... | https://api.stackexchange.com |
In computer science, we have often have to solve recurrence relations, that is find a closed form for a recursively defined sequence of numbers. When considering runtimes, we are often interested mainly in the sequence's asymptotic growth.
Examples are
The runtime of a tail-recursive function stepping downwards to $0... | Converting Full History to Limited History
This is a first step in solving recurrences where the value at any integer depends on the values at all smaller integers. Consider, for example, the recurrence
$$
T(n) = n + \frac{1}{n}\sum_{k=1}^n \big(T(k-1) + T(n-k)\big)
$$
which arises in the analysis of randomized quicks... | https://api.stackexchange.com |
Need to understand the working of 'Embedding' layer in Keras library. I execute the following code in Python
import numpy as np
from keras.models import Sequential
from keras.layers import Embedding
model = Sequential()
model.add(Embedding(5, 2, input_length=5))
input_array = np.random.randint(5, size=(1, 5))
model... | In fact, the output vectors are not computed from the input using any mathematical operation. Instead, each input integer is used as the index to access a table that contains all possible vectors. That is the reason why you need to specify the size of the vocabulary as the first argument (so the table can be initialize... | https://api.stackexchange.com |
What is the difference between the three terms below?
percentile
quantile
quartile | 0 quartile = 0 quantile = 0 percentile
1 quartile = 0.25 quantile = 25 percentile
2 quartile = .5 quantile = 50 percentile (median)
3 quartile = .75 quantile = 75 percentile
4 quartile = 1 quantile = 100 percentile | https://api.stackexchange.com |
I spotted these two in my garden. What is this insect? He had firm control over the wasp and was just hanging on by one leg. He appeared to hold on until the wasp stopped moving and then flew away with it.
I live in Ohio (USA). The wasp was a bit less than 2cm long while the other insect was about 2.5cm long. | Given the large eyes, the almost non-existent antennae, the humped back, elongated abdomen and the wings, I'd say it is a robber fly.
It is one of many insects known to prey on wasps.
Note the description on the linked page:
This spindly piece of nastiness is a Robber Fly in the genus Diogmites. It seems that it's m... | https://api.stackexchange.com |
I have seen it mentioned that dependent type systems are not inferable, but are checkable. I was wondering if there is a simple explanation of why that is so, and whether or not there is there a limit of "dependency" where types can be indexed by values, below which type inference is possible and above which it is not? | For a rather simple version of dependent type theory, Gilles Dowek gave a proof of undecidability of typability in a non-empty context:
Gilles Dowek, The undecidability of typability in the $\lambda\Pi$-calculus
Which can be found here.
First let me clarify what is proven in that paper: he shows that in a dependent cal... | https://api.stackexchange.com |
Are there some good sites or blogs where I can keep myself updated on the latest news and papers about image and signal processing research, or I should just check out "classical" providers like IEEE Transactions, Elsevier, etc? | There are many for different subjects -
Efg's algorithm collection :
DSP Forum :
Data compression -
About rendering -
For all research papers -
Resources on Mp3 and Audio -
Steve on Image Processing -
Image Processing and Retrieval
Accelerated Image Processing -
The Digital Signal Processing Blog -
Noise & ... | https://api.stackexchange.com |
The state of the art of non-linearity is to use rectified linear units (ReLU) instead of sigmoid function in deep neural network. What are the advantages?
I know that training a network when ReLU is used would be faster, and it is more biological inspired, what are the other advantages? (That is, any disadvantages of u... | Two additional major benefits of ReLUs are sparsity and a reduced likelihood of vanishing gradient. But first recall the definition of a ReLU is $h = \max(0, a)$ where $a = Wx + b$.
One major benefit is the reduced likelihood of the gradient to vanish. This arises when $a > 0$. In this regime the gradient has a constan... | https://api.stackexchange.com |
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